U.S. Pat. No. 5,621,262 to Han, incorporated herein in its entirety by this reference, illustrates in its FIGS. 1 and 2 exemplary existing carbon brush holders. Both holders include (unlettered) caps, typically formed of plastic like material B of FIG. 1. Additionally shown in FIG. 2 are a brush C to which a lead is attached or embedded, with the lead in turn being connected to terminal G. An (unlettered) spring biases brush C (downward in the drawing) toward the surface of a rotating commutator, with the cap of the holder serving to compress the spring and effectively fix the position of one of its ends.
Also disclosed in the Han patent are various embodiments of a brush holder in which a flexible copper lead connects a brush to an element denoted a "brush terminal," which brush terminal in turn contacts an element called the "lead terminal." Like the brush holder of FIG. 2 of the Han patent, these other embodiments may contain a spring useful to bias the brush to contact the surface of a commutator. As illustrated in FIG. 15 of the Han patent, for example, the position of one end of the spring (the upper end shown in the drawing) is fixed by the brush terminal and underside of a cap screwed into the holder body, while its other end abuts a carbon brush. According to the Han patent, the cap is plastic and functions also to press together the lead and brush terminals.
Other commercially-available designs involving torsion springs include seventeen components, while those utilizing leaf and coil springs may contain as many as thirteen components. Typical coil-spring designs, for example, require not only a card and dual shunted brushes, but also two brush boxes, two coil springs, two lead wires, and four terminals (two to the brush boxes and two to external switches). Assembly of these coil-spring designs requires two repetitions of eight steps, including (1) inserting a spring into a brush box, (2) inserting a brush into the brush box, (3) bonding the shunt wire to the brush box, (4) bending the tab of the brush box to retain the brush and spring within the box, (5) bonding one end of a lead wire to a terminal (to the brush box), (6) bonding the other end of the lead wire to a terminal (to an external switch), (7) mounting the brush box assembly to a brush card, and (8) inserting a lead wire and terminal into a terminal of the brush box. Although assembly of existing leaf-spring designs necessitates two repetitions of fewer steps (six rather than eight), it nonetheless continues to require steps of bonding of lead wires and leaf springs to terminals or mounts and interconnecting the components via the terminals.